Abstract
S6K1 is a member of the AGC subfamily of serine-threonine protein kinases, whereby catalytic activation requires dual phosphorylation of critical residues in the conserved T-loop (T229) and hydrophobic motif (HM; T389) peptide regions of its catalytic kinase domain (residues 1-398). In addition to its kinase domain, S6K1 contains a C-terminal autoinhibitory domain (AID; residues 399-502), which prevents T-loop and HM phosphorylation; and autoinhibition is relieved on multi-site Ser-Thr phosphorylation of the AID (S411, S418, T421, and S424). Interestingly, 66 of the 104 C-terminal AID amino acid residues were computer predicted to exist in structurally disordered peptide regions, begetting interest as to how such dynamics could be coupled to autoregulation. To begin addressing this issue, we developed and optimized protocols for efficient AID expression and purification. Consistent with computer predictions, aberrant mobilities in both SDS-PAGE and size-exclusion chromatography, as well as low chemical shift dispersion in 1H-15N HSQC NMR spectra, indicated purified recombinant AID to be largely unfolded. Yet, trans-addition of purified AID effectively inhibited PDK1-catalyzed T-loop phosphorylation of a catalytic kinase domain construct of S6K1. Using an identical purification protocol, similar protein yields of a tetraphospho-mimic mutant AID(D2ED) construct were obtained; and this construct displayed only weak inhibition of PDK1-catalyzed T229 phosphorylation. Purification of the structurally 'disordered' and functional C-terminal AID and AID(D2ED) constructs will facilitate studies aimed to understand the role of conformational plasticity and protein phosphorylation in modulating autoregulatory domain-domain interactions.
| Original language | English |
|---|---|
| Pages (from-to) | 271-279 |
| Number of pages | 9 |
| Journal | Protein Expression and Purification |
| Volume | 57 |
| Issue number | 2 |
| DOIs | |
| State | Published - Feb 1 2008 |
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Keywords
- Autoinhibition
- Custom gene synthesis
- Disordered proteins
- Intrinsic disorder
- Minimal media
- PDK1
- Phosphoinositide-dependent protein kinase-1
- Proteolysis inhibition
ASJC Scopus subject areas
- Biochemistry
Cite this
Expression, purification, and characterization of a structurally disordered and functional C-terminal autoinhibitory domain (AID) of the 70 kDa 40S ribosomal protein S6 kinase-1 (S6K1). / Ragan, Timothy J.; Ross, Duncan B.; Keshwani, Malik M.; Harris, Thomas K.
In: Protein Expression and Purification, Vol. 57, No. 2, 01.02.2008, p. 271-279.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Expression, purification, and characterization of a structurally disordered and functional C-terminal autoinhibitory domain (AID) of the 70 kDa 40S ribosomal protein S6 kinase-1 (S6K1)
AU - Ragan, Timothy J.
AU - Ross, Duncan B.
AU - Keshwani, Malik M.
AU - Harris, Thomas K
PY - 2008/2/1
Y1 - 2008/2/1
N2 - S6K1 is a member of the AGC subfamily of serine-threonine protein kinases, whereby catalytic activation requires dual phosphorylation of critical residues in the conserved T-loop (T229) and hydrophobic motif (HM; T389) peptide regions of its catalytic kinase domain (residues 1-398). In addition to its kinase domain, S6K1 contains a C-terminal autoinhibitory domain (AID; residues 399-502), which prevents T-loop and HM phosphorylation; and autoinhibition is relieved on multi-site Ser-Thr phosphorylation of the AID (S411, S418, T421, and S424). Interestingly, 66 of the 104 C-terminal AID amino acid residues were computer predicted to exist in structurally disordered peptide regions, begetting interest as to how such dynamics could be coupled to autoregulation. To begin addressing this issue, we developed and optimized protocols for efficient AID expression and purification. Consistent with computer predictions, aberrant mobilities in both SDS-PAGE and size-exclusion chromatography, as well as low chemical shift dispersion in 1H-15N HSQC NMR spectra, indicated purified recombinant AID to be largely unfolded. Yet, trans-addition of purified AID effectively inhibited PDK1-catalyzed T-loop phosphorylation of a catalytic kinase domain construct of S6K1. Using an identical purification protocol, similar protein yields of a tetraphospho-mimic mutant AID(D2ED) construct were obtained; and this construct displayed only weak inhibition of PDK1-catalyzed T229 phosphorylation. Purification of the structurally 'disordered' and functional C-terminal AID and AID(D2ED) constructs will facilitate studies aimed to understand the role of conformational plasticity and protein phosphorylation in modulating autoregulatory domain-domain interactions.
AB - S6K1 is a member of the AGC subfamily of serine-threonine protein kinases, whereby catalytic activation requires dual phosphorylation of critical residues in the conserved T-loop (T229) and hydrophobic motif (HM; T389) peptide regions of its catalytic kinase domain (residues 1-398). In addition to its kinase domain, S6K1 contains a C-terminal autoinhibitory domain (AID; residues 399-502), which prevents T-loop and HM phosphorylation; and autoinhibition is relieved on multi-site Ser-Thr phosphorylation of the AID (S411, S418, T421, and S424). Interestingly, 66 of the 104 C-terminal AID amino acid residues were computer predicted to exist in structurally disordered peptide regions, begetting interest as to how such dynamics could be coupled to autoregulation. To begin addressing this issue, we developed and optimized protocols for efficient AID expression and purification. Consistent with computer predictions, aberrant mobilities in both SDS-PAGE and size-exclusion chromatography, as well as low chemical shift dispersion in 1H-15N HSQC NMR spectra, indicated purified recombinant AID to be largely unfolded. Yet, trans-addition of purified AID effectively inhibited PDK1-catalyzed T-loop phosphorylation of a catalytic kinase domain construct of S6K1. Using an identical purification protocol, similar protein yields of a tetraphospho-mimic mutant AID(D2ED) construct were obtained; and this construct displayed only weak inhibition of PDK1-catalyzed T229 phosphorylation. Purification of the structurally 'disordered' and functional C-terminal AID and AID(D2ED) constructs will facilitate studies aimed to understand the role of conformational plasticity and protein phosphorylation in modulating autoregulatory domain-domain interactions.
KW - Autoinhibition
KW - Custom gene synthesis
KW - Disordered proteins
KW - Intrinsic disorder
KW - Minimal media
KW - PDK1
KW - Phosphoinositide-dependent protein kinase-1
KW - Proteolysis inhibition
UR - http://www.scopus.com/inward/record.url?scp=37349113787&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=37349113787&partnerID=8YFLogxK
U2 - 10.1016/j.pep.2007.09.014
DO - 10.1016/j.pep.2007.09.014
M3 - Article
C2 - 17980619
AN - SCOPUS:37349113787
VL - 57
SP - 271
EP - 279
JO - Protein Expression and Purification
JF - Protein Expression and Purification
SN - 1046-5928
IS - 2
ER -